Generally, shift gear sets are provided to a synchromesh-type manual transmission apparatus in order to configure four to seven forward shift stages. Each of the shift gear sets is selectively engaged by means of a synchromesh mechanism. An operating device of the manual transmission apparatus for performing a shift operation includes fork shafts, each of which operates the corresponding synchromesh mechanism, a shift-and-select shaft for selecting and driving one of the fork shafts, a gear lever, which is operated by a driver, and an operation transmitting mechanism for transmitting an operation force applied to the gear lever to the shift-and-select shaft. Generally, the shift-and-select shaft is configured so as to rotate in a circumferential direction thereof and so as to move in an axial direction thereof. More specifically, in a case where the shift-and-select shaft rotates in the circumferential direction thereof in order to select one of the fork shafts (a select operation), the shift-and-select shaft moves in the axial direction thereof in order to move the selected fork shaft in an axial direction thereof (a shift operation). On the other hand, in a case where the shift-and-select shaft moves in the axial direction thereof in order to select one of the fork shafts (a select operation), the shift-and-select shaft rotates in the circumferential direction thereof in order to move the selected fork shaft in an axial direction thereof (a shift operation). In the synchromesh mechanism, which corresponds to the selected fork shaft (a selected gear stage), when a sleeve of the selected synchromesh mechanism is shift-operated by the selected fork shaft, the synchronizer ring (an input side portion) and the selected gear (an output side portion) are frictionally engaged by an inner slide mechanism of the synchromesh mechanism, thereby synchronizing a rotation of the selected gear and a rotation of an output side shaft of the manual transmission apparatus. Accordingly, the sleeve and the selected gear are fittedly connected by an engaging mechanism of the synchromesh mechanism via the synchronizer ring and the selected shift stage is established. The operation force necessary in a process of the shift operation of the synchromesh mechanism is not constant. Furthermore, a reaction force may be generated when the synchronizer ring is frictionally engaged with the selected gear or when the sleeve is fittedly connected with the selected gear, and such reaction force may be transmitted to the gear lever.
A demand for enhancing a shift feeling when performing the shift operation by controlling changes in the operation force or the reaction force of the synchromesh mechanism is increased. A shift device of a manual transmission apparatus for a vehicle, which is disclosed in JP2003-106449A, attempts to enhance the shift feeling by using inertial action, which is generated when pivoting an outer lever, which pivots around a shift-and-select shaft and to which an inertia lever and an inertia mass are provided. Furthermore, according to a shift mechanism for a manual transmission apparatus, which is disclosed in JP2008-32158A, an inertia mass is configured so as to be relatively displaced on an inertia lever, which pivots around a shift-and-select shaft, so that an inertia generated when a shift operation is performed by a driver is increased and the inertia when the shift operation is not performed by the driver is decreased in order to decrease vibration (oscillation) transmitted to a gear lever.
However, the shift device disclosed in JP2003-106449A and the shift mechanism disclosed in JP2008-32158A are adaptable to an operating device for a manual transmission apparatus, which is configured to shift-operate a fork shaft by rotating the shift-and-select shaft in a circumferential direction thereof. Therefore, the shift device disclosed in JP2003-106449A and the shift mechanism disclosed in JP2008-32158A are not adaptable to an operating device for a manual transmission apparatus, which is configured to shift-operate the fork shaft by moving the shift-and-select shaft in an axial direction thereof.
Furthermore, the inertia lever and the inertia mass are assembled to the operating device so as to ensure a certain clearance therebetween. In order to smoothly operate the inertia lever and the inertia mass. Additionally, the clearance is considered to be necessary in view of allowance when producing the inertia lever and the inertia mass and assembling operability. However, because the clearance is ensured at the operating device, delay or backlash may occur in the inertial action, which may result in failing to generate a sufficient shift feeling. For example, in a case where a moving speed of the shift-and-select shaft in the axial direction is reduced, the inertia lever or the inertia mass move in response to a movement of the shift-and-select shaft so as to delay for a time necessary for the inertia lever or the inertia mass to move within the clearance. Therefore, while the inertia lever or the inertia mass moves within the clearance, the inertial action is not generated, and the reaction force is directly transmitted to the gear lever, thereby deteriorating the shift feeling.
A need thus exists to provide an operating device for a manual transmission apparatus which is not susceptible to the drawback mentioned above.